/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/*
 * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 * This file is part of the lwIP TCP/IP stack.
 *
 * Author: Adam Dunkels <adam@sics.se>
 *
 */

/**
 * @file
 * Sequential API External module
 *
 */

/* This is the part of the API that is linked with
   the application */

#include <net/lwip/opt.h>

#if LWIP_NETCONN				/* don't build if not configured for use in lwipopts.h */

#include <net/lwip/api.h>
#include <net/lwip/tcpip.h>
#include <net/lwip/memp.h>

#include <net/lwip/ipv4/ip.h>
#include <net/lwip/raw.h>
#include <net/lwip/udp.h>
#include <net/lwip/tcp.h>

#include <string.h>

/**
 * Create a new netconn (of a specific type) that has a callback function.
 * The corresponding pcb is also created.
 *
 * @param t the type of 'connection' to create (@see enum netconn_type)
 * @param proto the IP protocol for RAW IP pcbs
 * @param callback a function to call on status changes (RX available, TX'ed)
 * @return a newly allocated struct netconn or
 *         NULL on memory error
 */
struct netconn *netconn_new_with_proto_and_callback(enum netconn_type t, u8_t proto, netconn_callback callback)
{
	struct netconn *conn;
	struct api_msg msg;
	LWIP_DEBUGF(API_LIB_DEBUG, ("Entry \n"));
	conn = netconn_alloc(t, callback);
	if (conn != NULL) {
		msg.function = do_newconn;
		msg.msg.msg.n.proto = proto;
		msg.msg.conn = conn;
		if (TCPIP_APIMSG(&msg) != ERR_OK) {
			LWIP_ASSERT("freeing conn without freeing pcb", conn->pcb.tcp == NULL);
			LWIP_ASSERT("conn has no op_completed", sys_sem_valid(&conn->op_completed));
			LWIP_ASSERT("conn has no recvmbox", sys_mbox_valid(&conn->recvmbox));
#if LWIP_TCP
			LWIP_ASSERT("conn->acceptmbox shouldn't exist", !sys_mbox_valid(&conn->acceptmbox));
#endif							/* LWIP_TCP */
			sys_sem_free(&conn->op_completed);
			sys_mbox_free(&conn->recvmbox);
			memp_free(MEMP_NETCONN, conn);
			return NULL;
			LWIP_DEBUGF(API_LIB_DEBUG, ("Exit without conn \n"));
		}
	}
	LWIP_DEBUGF(API_LIB_DEBUG, ("Exit with conn \n"));
	return conn;
}

/**
 * Close a netconn 'connection' and free its resources.
 * UDP and RAW connection are completely closed, TCP pcbs might still be in a waitstate
 * after this returns.
 *
 * @param conn the netconn to delete
 * @return ERR_OK if the connection was deleted
 */
err_t netconn_delete(struct netconn *conn)
{
	struct api_msg msg;

	/* No ASSERT here because possible to get a (conn == NULL) if we got an accept error */
	if (conn == NULL) {
		return ERR_OK;
	}

	SYS_ARCH_DECL_PROTECT(lev);
	SYS_ARCH_PROTECT(lev);
	conn->crefs--;
	if (conn->crefs > 0) {
		SYS_ARCH_UNPROTECT(lev);
		return ERR_OK;
	}
	SYS_ARCH_UNPROTECT(lev);

	msg.function = do_delconn;
	msg.msg.conn = conn;
	tcpip_apimsg(&msg);

	netconn_free(conn);

	/* don't care for return value of do_delconn since it only calls void functions */

	return ERR_OK;
}

/**
 * Get the local or remote IP address and port of a netconn.
 * For RAW netconns, this returns the protocol instead of a port!
 *
 * @param conn the netconn to query
 * @param addr a pointer to which to save the IP address
 * @param port a pointer to which to save the port (or protocol for RAW)
 * @param local 1 to get the local IP address, 0 to get the remote one
 * @return ERR_CONN for invalid connections
 *         ERR_OK if the information was retrieved
 */
err_t netconn_getaddr(struct netconn *conn, ip_addr_t *addr, u16_t *port, u8_t local)
{
	struct api_msg msg;
	err_t err;

	LWIP_ERROR("netconn_getaddr: invalid conn", (conn != NULL), return ERR_ARG;);
	LWIP_ERROR("netconn_getaddr: invalid addr", (addr != NULL), return ERR_ARG;);
	LWIP_ERROR("netconn_getaddr: invalid port", (port != NULL), return ERR_ARG;);

	msg.function = do_getaddr;
	msg.msg.conn = conn;
	msg.msg.msg.ad.ipaddr = addr;
	msg.msg.msg.ad.port = port;
	msg.msg.msg.ad.local = local;
	err = TCPIP_APIMSG(&msg);

	NETCONN_SET_SAFE_ERR(conn, err);
	return err;
}

/**
 * Bind a netconn to a specific local IP address and port.
 * Binding one netconn twice might not always be checked correctly!
 *
 * @param conn the netconn to bind
 * @param addr the local IP address to bind the netconn to (use IP_ADDR_ANY
 *             to bind to all addresses)
 * @param port the local port to bind the netconn to (not used for RAW)
 * @return ERR_OK if bound, any other err_t on failure
 */
err_t netconn_bind(struct netconn *conn, ip_addr_t *addr, u16_t port)
{
	struct api_msg msg;
	err_t err;

	LWIP_ERROR("netconn_bind: invalid conn", (conn != NULL), return ERR_ARG;);

	msg.function = do_bind;
	msg.msg.conn = conn;
	msg.msg.msg.bc.ipaddr = addr;
	msg.msg.msg.bc.port = port;
	err = TCPIP_APIMSG(&msg);

	NETCONN_SET_SAFE_ERR(conn, err);
	return err;
}

/**
 * Connect a netconn to a specific remote IP address and port.
 *
 * @param conn the netconn to connect
 * @param addr the remote IP address to connect to
 * @param port the remote port to connect to (no used for RAW)
 * @return ERR_OK if connected, return value of tcp_/udp_/raw_connect otherwise
 */
err_t netconn_connect(struct netconn *conn, ip_addr_t *addr, u16_t port)
{
	struct api_msg msg;
	err_t err;

	LWIP_ERROR("netconn_connect: invalid conn", (conn != NULL), return ERR_ARG;);

	msg.function = do_connect;
	msg.msg.conn = conn;
	msg.msg.msg.bc.ipaddr = addr;
	msg.msg.msg.bc.port = port;
	/* This is the only function which need to not block tcpip_thread */
	err = tcpip_apimsg(&msg);

	NETCONN_SET_SAFE_ERR(conn, err);
	return err;
}

/**
 * Disconnect a netconn from its current peer (only valid for UDP netconns).
 *
 * @param conn the netconn to disconnect
 * @return TODO: return value is not set here...
 */
err_t netconn_disconnect(struct netconn *conn)
{
	struct api_msg msg;
	err_t err;

	LWIP_ERROR("netconn_disconnect: invalid conn", (conn != NULL), return ERR_ARG;);

	msg.function = do_disconnect;
	msg.msg.conn = conn;
	err = TCPIP_APIMSG(&msg);

	NETCONN_SET_SAFE_ERR(conn, err);
	return err;
}

/**
 * Set a TCP netconn into listen mode
 *
 * @param conn the tcp netconn to set to listen mode
 * @param backlog the listen backlog, only used if TCP_LISTEN_BACKLOG==1
 * @return ERR_OK if the netconn was set to listen (UDP and RAW netconns
 *         don't return any error (yet?))
 */
err_t netconn_listen_with_backlog(struct netconn *conn, u8_t backlog)
{
#if LWIP_TCP
	struct api_msg msg;
	err_t err;

	/* This does no harm. If TCP_LISTEN_BACKLOG is off, backlog is unused. */
	LWIP_UNUSED_ARG(backlog);

	LWIP_ERROR("netconn_listen: invalid conn", (conn != NULL), return ERR_ARG;);

	msg.function = do_listen;
	msg.msg.conn = conn;
#if TCP_LISTEN_BACKLOG
	msg.msg.msg.lb.backlog = backlog;
#endif							/* TCP_LISTEN_BACKLOG */
	err = TCPIP_APIMSG(&msg);

	NETCONN_SET_SAFE_ERR(conn, err);
	return err;
#else							/* LWIP_TCP */
	LWIP_UNUSED_ARG(conn);
	LWIP_UNUSED_ARG(backlog);
	return ERR_ARG;
#endif							/* LWIP_TCP */
}

/**
 * Accept a new connection on a TCP listening netconn.
 *
 * @param conn the TCP listen netconn
 * @param new_conn pointer where the new connection is stored
 * @return ERR_OK if a new connection has been received or an error
 *                code otherwise
 */
err_t netconn_accept(struct netconn *conn, struct netconn **new_conn)
{
#if LWIP_TCP
	struct netconn *newconn = NULL;
	LWIP_DEBUGF(TCPIP_DEBUG, ("NULL == newconn %d \n", NULL == newconn));
	err_t err;
#if TCP_LISTEN_BACKLOG
	struct api_msg msg;
#endif							/* TCP_LISTEN_BACKLOG */

	LWIP_ERROR("netconn_accept: invalid pointer", (new_conn != NULL), return ERR_ARG;);
	*new_conn = NULL;
	LWIP_ERROR("netconn_accept: invalid conn", (conn != NULL), return ERR_ARG;);
	LWIP_ERROR("netconn_accept: invalid acceptmbox", sys_mbox_valid(&conn->acceptmbox), return ERR_ARG;);

	err = conn->last_err;
	if (ERR_IS_FATAL(err)) {
		/* don't recv on fatal errors: this might block the application task
		   waiting on acceptmbox forever! */
		return err;
	}
#if LWIP_SO_RCVTIMEO
	if (sys_arch_mbox_fetch(&conn->acceptmbox, (void **)&newconn, conn->recv_timeout) == SYS_ARCH_TIMEOUT) {
		NETCONN_SET_SAFE_ERR(conn, ERR_TIMEOUT);
		return ERR_TIMEOUT;
	}
#else
	sys_arch_mbox_fetch(&conn->acceptmbox, (void **)&newconn, 0);
#endif							/* LWIP_SO_RCVTIMEO */
	/* Register event with callback */
	API_EVENT(conn, NETCONN_EVT_RCVMINUS, 0);

	if (newconn == NULL) {
		/* connection has been aborted */
		NETCONN_SET_SAFE_ERR(conn, ERR_ABRT);
		return ERR_ABRT;
	}
#if TCP_LISTEN_BACKLOG
	/* Let the stack know that we have accepted the connection. */
	msg.function = do_recv;
	msg.msg.conn = conn;
	/* don't care for the return value of do_recv */
	TCPIP_APIMSG(&msg);
#endif							/* TCP_LISTEN_BACKLOG */

	*new_conn = newconn;
	/* don't set conn->last_err: it's only ERR_OK, anyway */
	return ERR_OK;
#else							/* LWIP_TCP */
	LWIP_UNUSED_ARG(conn);
	LWIP_UNUSED_ARG(new_conn);
	return ERR_ARG;
#endif							/* LWIP_TCP */
}

/**
 * Receive data: actual implementation that doesn't care whether pbuf or netbuf
 * is received
 *
 * @param conn the netconn from which to receive data
 * @param new_buf pointer where a new pbuf/netbuf is stored when received data
 * @return ERR_OK if data has been received, an error code otherwise (timeout,
 *                memory error or another error)
 */
static err_t netconn_recv_data(struct netconn *conn, void **new_buf)
{
	void *buf = NULL;
	u16_t len;
	err_t err;
#if LWIP_TCP
	struct api_msg msg;
#endif							/* LWIP_TCP */

	LWIP_ERROR("netconn_recv: invalid pointer", (new_buf != NULL), return ERR_ARG;);
	*new_buf = NULL;
	LWIP_ERROR("netconn_recv: invalid conn", (conn != NULL), return ERR_ARG;);
	LWIP_ERROR("netconn_accept: invalid recvmbox", sys_mbox_valid(&conn->recvmbox), return ERR_CONN;);

	err = conn->last_err;
	if (ERR_IS_FATAL(err)) {
		/* don't recv on fatal errors: this might block the application task
		   waiting on recvmbox forever! */
		/* @todo: this does not allow us to fetch data that has been put into recvmbox
		   before the fatal error occurred - is that a problem? */
		return err;
	}
#if LWIP_SO_RCVTIMEO
	if (sys_arch_mbox_fetch(&conn->recvmbox, &buf, conn->recv_timeout) == SYS_ARCH_TIMEOUT) {
		NETCONN_SET_SAFE_ERR(conn, ERR_TIMEOUT);
		return ERR_TIMEOUT;
	}
#else
	sys_arch_mbox_fetch(&conn->recvmbox, &buf, 0);
#endif							/* LWIP_SO_RCVTIMEO */

#if LWIP_TCP
#if (LWIP_UDP || LWIP_RAW)
	if (conn->type == NETCONN_TCP)
#endif							/* (LWIP_UDP || LWIP_RAW) */
	{
		if (!netconn_get_noautorecved(conn) || (buf == NULL)) {
			/* Let the stack know that we have taken the data. */
			/* TODO: Speedup: Don't block and wait for the answer here
			   (to prevent multiple thread-switches). */
			msg.function = do_recv;
			msg.msg.conn = conn;
			if (buf != NULL) {
				msg.msg.msg.r.len = ((struct pbuf *)buf)->tot_len;
			} else {
				msg.msg.msg.r.len = 1;
			}
			/* don't care for the return value of do_recv */
			TCPIP_APIMSG(&msg);
		}

		/* If we are closed, we indicate that we no longer wish to use the socket */
		if (buf == NULL) {
			API_EVENT(conn, NETCONN_EVT_RCVMINUS, 0);
			/* Avoid to lose any previous error code */
			NETCONN_SET_SAFE_ERR(conn, ERR_CLSD);
			return ERR_CLSD;
		}
		len = ((struct pbuf *)buf)->tot_len;
	}
#endif							/* LWIP_TCP */
#if LWIP_TCP && (LWIP_UDP || LWIP_RAW)
	else
#endif							/* LWIP_TCP && (LWIP_UDP || LWIP_RAW) */
#if (LWIP_UDP || LWIP_RAW)
	{
		LWIP_ASSERT("buf != NULL", buf != NULL);
		len = netbuf_len((struct netbuf *)buf);
	}
#endif							/* (LWIP_UDP || LWIP_RAW) */

#if LWIP_SO_RCVBUF
	SYS_ARCH_DEC(conn->recv_avail, len);
#endif							/* LWIP_SO_RCVBUF */
	/* Register event with callback */
	API_EVENT(conn, NETCONN_EVT_RCVMINUS, len);

	LWIP_DEBUGF(API_LIB_DEBUG, ("netconn_recv_data: received %p, len=%" U16_F "\n", buf, len));

	*new_buf = buf;
	/* don't set conn->last_err: it's only ERR_OK, anyway */
	return ERR_OK;
}

/**
 * Receive data (in form of a pbuf) from a TCP netconn
 *
 * @param conn the netconn from which to receive data
 * @param new_buf pointer where a new pbuf is stored when received data
 * @return ERR_OK if data has been received, an error code otherwise (timeout,
 *                memory error or another error)
 *         ERR_ARG if conn is not a TCP netconn
 */
err_t netconn_recv_tcp_pbuf(struct netconn *conn, struct pbuf **new_buf)
{
	LWIP_ERROR("netconn_recv: invalid conn", (conn != NULL) && netconn_type(conn) == NETCONN_TCP, return ERR_ARG;);

	return netconn_recv_data(conn, (void **)new_buf);
}

/**
 * Receive data (in form of a netbuf containing a packet buffer) from a netconn
 *
 * @param conn the netconn from which to receive data
 * @param new_buf pointer where a new netbuf is stored when received data
 * @return ERR_OK if data has been received, an error code otherwise (timeout,
 *                memory error or another error)
 */
err_t netconn_recv(struct netconn *conn, struct netbuf **new_buf)
{
#if LWIP_TCP
	struct netbuf *buf = NULL;
	err_t err;
#endif							/* LWIP_TCP */

	LWIP_ERROR("netconn_recv: invalid pointer", (new_buf != NULL), return ERR_ARG;);
	*new_buf = NULL;
	LWIP_ERROR("netconn_recv: invalid conn", (conn != NULL), return ERR_ARG;);
	LWIP_ERROR("netconn_accept: invalid recvmbox", sys_mbox_valid(&conn->recvmbox), return ERR_CONN;);

#if LWIP_TCP
#if (LWIP_UDP || LWIP_RAW)
	if (conn->type == NETCONN_TCP)
#endif							/* (LWIP_UDP || LWIP_RAW) */
	{
		struct pbuf *p = NULL;
		/* This is not a listening netconn, since recvmbox is set */

		buf = (struct netbuf *)memp_malloc(MEMP_NETBUF);
		if (buf == NULL) {
			NETCONN_SET_SAFE_ERR(conn, ERR_MEM);
			return ERR_MEM;
		}

		err = netconn_recv_data(conn, (void **)&p);
		if (err != ERR_OK) {
			memp_free(MEMP_NETBUF, buf);
			return err;
		}
		LWIP_ASSERT("p != NULL", p != NULL);

		buf->p = p;
		buf->ptr = p;
		buf->port = 0;
		ip_addr_set_any(&buf->addr);
		*new_buf = buf;
		/* don't set conn->last_err: it's only ERR_OK, anyway */
		return ERR_OK;
	}
#endif							/* LWIP_TCP */
#if LWIP_TCP && (LWIP_UDP || LWIP_RAW)
	else
#endif							/* LWIP_TCP && (LWIP_UDP || LWIP_RAW) */
	{
#if (LWIP_UDP || LWIP_RAW)
		return netconn_recv_data(conn, (void **)new_buf);
#endif							/* (LWIP_UDP || LWIP_RAW) */
	}
}

/**
 * TCP: update the receive window: by calling this, the application
 * tells the stack that it has processed data and is able to accept
 * new data.
 * ATTENTION: use with care, this is mainly used for sockets!
 * Can only be used when calling netconn_set_noautorecved(conn, 1) before.
 *
 * @param conn the netconn for which to update the receive window
 * @param length amount of data processed (ATTENTION: this must be accurate!)
 */
void netconn_recved(struct netconn *conn, u32_t length)
{
#if LWIP_TCP
	if ((conn != NULL) && (conn->type == NETCONN_TCP) && (netconn_get_noautorecved(conn))) {
		struct api_msg msg;
		/* Let the stack know that we have taken the data. */
		/* TODO: Speedup: Don't block and wait for the answer here
		   (to prevent multiple thread-switches). */
		msg.function = do_recv;
		msg.msg.conn = conn;
		msg.msg.msg.r.len = length;
		/* don't care for the return value of do_recv */
		TCPIP_APIMSG(&msg);
	}
#else							/* LWIP_TCP */
	LWIP_UNUSED_ARG(conn);
	LWIP_UNUSED_ARG(length);
#endif							/* LWIP_TCP */
}

/**
 * Send data (in form of a netbuf) to a specific remote IP address and port.
 * Only to be used for UDP and RAW netconns (not TCP).
 *
 * @param conn the netconn over which to send data
 * @param buf a netbuf containing the data to send
 * @param addr the remote IP address to which to send the data
 * @param port the remote port to which to send the data
 * @return ERR_OK if data was sent, any other err_t on error
 */
err_t netconn_sendto(struct netconn *conn, struct netbuf *buf, ip_addr_t *addr, u16_t port)
{
	if (buf != NULL) {
		ip_addr_set(&buf->addr, addr);
		buf->port = port;
		return netconn_send(conn, buf);
	}
	return ERR_VAL;
}

/**
 * Send data over a UDP or RAW netconn (that is already connected).
 *
 * @param conn the UDP or RAW netconn over which to send data
 * @param buf a netbuf containing the data to send
 * @return ERR_OK if data was sent, any other err_t on error
 */
err_t netconn_send(struct netconn *conn, struct netbuf *buf)
{
	struct api_msg msg;
	err_t err;

	LWIP_ERROR("netconn_send: invalid conn", (conn != NULL), return ERR_ARG;);

	LWIP_DEBUGF(API_LIB_DEBUG, ("netconn_send: sending %" U16_F " bytes\n", buf->p->tot_len));
	msg.function = do_send;
	msg.msg.conn = conn;
	msg.msg.msg.b = buf;

	err = TCPIP_APIMSG(&msg);
	NETCONN_SET_SAFE_ERR(conn, err);
	return err;
}

/**
 * Send data over a TCP netconn.
 *
 * @param conn the TCP netconn over which to send data
 * @param dataptr pointer to the application buffer that contains the data to send
 * @param size size of the application data to send
 * @param apiflags combination of following flags :
 * - NETCONN_COPY: data will be copied into memory belonging to the stack
 * - NETCONN_MORE: for TCP connection, PSH flag will be set on last segment sent
 * - NETCONN_DONTBLOCK: only write the data if all dat can be written at once
 * @param bytes_written pointer to a location that receives the number of written bytes
 * @return ERR_OK if data was sent, any other err_t on error
 */
err_t netconn_write_partly(struct netconn *conn, const void *dataptr, size_t size, u8_t apiflags, size_t *bytes_written)
{
	struct api_msg msg;
	err_t err;
	u8_t dontblock;

	LWIP_ERROR("netconn_write: invalid conn", (conn != NULL), return ERR_ARG;);
	LWIP_ERROR("netconn_write: invalid conn->type", (conn->type == NETCONN_TCP), return ERR_VAL;);
	if (size == 0) {
		return ERR_OK;
	}
	dontblock = netconn_is_nonblocking(conn) || (apiflags & NETCONN_DONTBLOCK);
	if (dontblock && !bytes_written) {
		/* This implies netconn_write() cannot be used for non-blocking send, since
		   it has no way to return the number of bytes written. */
		return ERR_VAL;
	}

	/* non-blocking write sends as much  */
	msg.function = do_write;
	msg.msg.conn = conn;
	msg.msg.msg.w.dataptr = dataptr;
	msg.msg.msg.w.apiflags = apiflags;
	msg.msg.msg.w.len = size;
#if LWIP_SO_SNDTIMEO
	if (conn->send_timeout != 0) {
		/* get the time we started, which is later compared to
		   sys_now() + conn->send_timeout */
		msg.msg.msg.w.time_started = sys_now();
	} else {
		msg.msg.msg.w.time_started = 0;
	}
#endif							/* LWIP_SO_SNDTIMEO */

	/* For locking the core: this _can_ be delayed on low memory/low send buffer,
	   but if it is, this is done inside api_msg.c:do_write(), so we can use the
	   non-blocking version here. */
	err = TCPIP_APIMSG(&msg);
	if ((err == ERR_OK) && (bytes_written != NULL)) {
		if (dontblock
#if LWIP_SO_SNDTIMEO
			|| (conn->send_timeout != 0)
#endif							/* LWIP_SO_SNDTIMEO */
		   ) {
			/* nonblocking write: maybe the data has been sent partly */
			*bytes_written = msg.msg.msg.w.len;
		} else {
			/* blocking call succeeded: all data has been sent if it */
			*bytes_written = size;
		}
	}

	NETCONN_SET_SAFE_ERR(conn, err);
	return err;
}

/**
 * Close ot shutdown a TCP netconn (doesn't delete it).
 *
 * @param conn the TCP netconn to close or shutdown
 * @param how fully close or only shutdown one side?
 * @return ERR_OK if the netconn was closed, any other err_t on error
 */
static err_t netconn_close_shutdown(struct netconn *conn, u8_t how)
{
	struct api_msg msg;
	err_t err;

	LWIP_ERROR("netconn_close: invalid conn", (conn != NULL), return ERR_ARG;);

	msg.function = do_close;
	msg.msg.conn = conn;
	/* shutting down both ends is the same as closing */
	msg.msg.msg.sd.shut = how;
	/* because of the LWIP_TCPIP_CORE_LOCKING implementation of do_close,
	   don't use TCPIP_APIMSG here */
	err = tcpip_apimsg(&msg);

	NETCONN_SET_SAFE_ERR(conn, err);
	return err;
}

/**
 * Close a TCP netconn (doesn't delete it).
 *
 * @param conn the TCP netconn to close
 * @return ERR_OK if the netconn was closed, any other err_t on error
 */
err_t netconn_close(struct netconn *conn)
{
	/* shutting down both ends is the same as closing */
	return netconn_close_shutdown(conn, NETCONN_SHUT_RDWR);
}

/**
 * Shut down one or both sides of a TCP netconn (doesn't delete it).
 *
 * @param conn the TCP netconn to shut down
 * @return ERR_OK if the netconn was closed, any other err_t on error
 */
err_t netconn_shutdown(struct netconn *conn, u8_t shut_rx, u8_t shut_tx)
{
	return netconn_close_shutdown(conn, (shut_rx ? NETCONN_SHUT_RD : 0) | (shut_tx ? NETCONN_SHUT_WR : 0));
}

#if LWIP_IGMP
/**
 * Join multicast groups for UDP netconns.
 *
 * @param conn the UDP netconn for which to change multicast addresses
 * @param multiaddr IP address of the multicast group to join or leave
 * @param netif_addr the IP address of the network interface on which to send
 *                  the igmp message
 * @param join_or_leave flag whether to send a join- or leave-message
 * @return ERR_OK if the action was taken, any err_t on error
 */
err_t netconn_join_leave_group(struct netconn *conn, ip_addr_t *multiaddr, ip_addr_t *netif_addr, enum netconn_igmp join_or_leave)
{
	struct api_msg msg;
	err_t err;

	LWIP_ERROR("netconn_join_leave_group: invalid conn", (conn != NULL), return ERR_ARG;);

	msg.function = do_join_leave_group;
	msg.msg.conn = conn;
	msg.msg.msg.jl.multiaddr = multiaddr;
	msg.msg.msg.jl.netif_addr = netif_addr;
	msg.msg.msg.jl.join_or_leave = join_or_leave;
	err = TCPIP_APIMSG(&msg);

	NETCONN_SET_SAFE_ERR(conn, err);
	return err;
}
#endif							/* LWIP_IGMP */

#endif							/* LWIP_NETCONN */
